The purpose of this program is to determine the manner in which the central nervous system controls brainstem somatic reflex activity during different behavioral states. In the adult cat two areas of the central nervous system, the reticular core of the brainstem and the cerebral cortex, are of essential importance in sensory, motor and integrative activities and play a major role in almost all aspects of behavior. These areas also exert a pattern of both inhibition and excitation upon the brainstem masseteric and digastric reflexes during the states of sleep and wakefulness. Since the somatic reflex is a basic component of all behavioral states and a sensitive indicator of central neural activity, a study of the factors which control it is of basic scientific importance. The study of somatic reflexes is also of clinical relevance, for variations in activity are pathonomonic of a variety of neurological abnormalities. When the central neural mechanisms which are responsible for their modulation are better known, we will be able to diagnose and treat neurological disorders more effectively. In order to develop a better understanding of the state-dependent control of somatic reflex activity the following projects will be carried out: Project 1: State-dependent modulation of brainstem somatic reflex activity. Project 2: Mesencephalic and bulbar reticular control of reflex activity. Project 3: Motor, sensory, and orbital cortical modulation of reflex activity. Project 4: Recording of single and multiple unit activity. Project 5: Central neural correlates of conditioned somatic reflex activity. Project 6: Effect of reticular and cortical lesions upon reflex activity. Project 7: Central neural control of reflex activity during immobilization (Flaxedil).